Abstract

After a hole injection layer is inserted into a polymer light-emitting diode(PLED), the positive polaron is easily injected into the polymer layer. An applied electrical field drives the positive polaron to approach and collide with the nonemissive triplet exciton. The collision between the positive polaron and neutral triplet exciton induces the exciton to emit light. Based on this physical picture, the maximum quantum efficiency of the PLEDs, 61.6%, is consistent with the experimental result of 60%. With the help of an external magnetic field, a structure of PLEDs with high electroluminescent efficiency is designed.

Received 27 July 2009Accepted 03 September 2009Published online 13 October 2009

Acknowledgments:

We thank Shi-Yang Liu and Xin Sun for helpful discussions. Sheng Li also thanks R. B. Tao for a visit to the Center for Quantum Manipulation at Fudan University. This work was supported by the National Science Foundation of China under Grant No. 20804039 and the Zhejiang Provincial Natural Science Foundation of China under Grant No. Y4080300.